The purpose of this invention is to provide a speaker system that is compact and light in weight, with excellent frequency response characteristics and low distortion, that is capable of handling comparatively large amounts of audio power, and can be manufactured economically.
Conventional speaker systems are usually high in cost and consist of two-types, the totally enclosed type and the bass-reflex type and usual practice is to employ several types of speaker-units with characteristics designed to handle the low, middle, and high frequencies because of the difficulty in obtaining speaker-units with good response characteristics that can handle the entire audio spectrum. However, when several units are employed to cover the frequency spectrum, interference between the speaker-units at their cross-over frequency bands causes frequency response and other forms of distortion, which tend to affect the overall performance of the speaker system.
Conventional speaker enclosures including the totally enclosed, and the bass-reflex type suffer from the effects of sound pressure released from the openings at the back-side of the speaker-unit, in particular interference between sound pressure from the left and right sides of the unit that develops inside the enclosure and results in a rise in the acoustical impedance causes the phenomenon of `booming`, as well as, a tendancy for the enclosure walls to vibrate, and thereby tends to ruin the system's acoustical characteristics. Consequently, conventional speaker enclosure systems, including high-priced systems have failed to be compact in size and light in weight, and have large power handling capacity with excellent performance characteristics such as good frequency response and low distortion etc.
Recently, the general trend is for speaker-units with smaller size radiators. Consequently, there is a rising demand for compact speaker enclosure systems with excellent acoustical characteristics. However, the conventional design of speaker enclosures does not permit lowering of the low-end frequency response when the enclosure volume is decreased, thus, if the diameter of the speaker-unit is halved, the low-end acoustical output will be reduced by 12 dB and an audio power increase of several fold would be required to obtain the original acoustical output level.
Moreover, with a small size speaker-unit, the low-end cut-off frequency is relatively high, and the effective mass of the unit's vibrating system must be increased in order to lower its cut-off frequency, which in effect lowers the speaker's over-all efficiency.
Furthermore, in conventional speaker enclosure systems in which several different sized speaker-units are employed, elimination of the afore-described interference effect; caused by the acoustical pressure at the back-side of the speaker-units by effectively directing pressure from the left and right sides of the units toward the front has not been successful, even with bass-reflex type enclosures.